Piston assembly, fluid pressure cylinder, method for manufacturing piston assembly

Abstract

A piston main body in a piston assembly of a fluid pressure cylinder includes a first piston member and a second piston member including a plate-shaped member. The first piston member and the second piston member are joined in a state overlapping in the axial direction of a piston rod. The second piston member is not provided with a hole that passes through in the plate thickness direction.

The invention claimed is: 
     
       1. A piston assembly comprising:
 a piston main body; and 
 a piston rod joined to the piston main body, wherein: 
 the piston rod includes a cylindrical body portion; 
 the piston main body includes a first piston member and a second piston member which are constituted from plate-like members; 
 the first piston member and the second piston member are joined mutually under a condition of being superimposed in an axial direction of the piston rod; 
 a seal installation groove that extends in a circumferential direction is formed between an outer peripheral edge of the first piston member and an outer peripheral edge of the second piston member; 
 a through hole is provided in the first piston member so as to penetrate in a plate thickness direction thereof; 
 the second piston member has, over the entirety thereof, a plate thickness that is smaller than an outer diameter of the piston rod; 
 a fitting portion is provided on a proximal end of the cylindrical body portion to project from the proximal end of the piston rod in the axial direction of the piston rod, the fitting portion being fitted in the through hole; 
 the fitting portion has an outer diameter which is smaller than that of the cylindrical body portion and the fitting portion has an end surface that is joined to the second piston member by welding, 
 the end surface of the fitting portion is joined with an end surface of the second piston member located on a side of the second piston member that faces toward the first piston member; 
 the end surfaces of the fitting portion and the second piston member that are joined with each other are perpendicular to an axis of the piston rod; and 
 the outer diameter of the fitting portion is the same as, or slightly smaller than, the inner diameter of the through hole, 
 wherein one of the first piston member and the second piston member includes: 
 a first radial direction portion that extends in a radial direction perpendicular to the axis of the piston rod; 
 an axial direction portion that extends parallel to the axis of the piston rod, projects from an outer end of the first radial direction portion to a direction away from the other one of the first piston member and the second piston member, and includes 
 a first end portion that is located at an end connected to the outer end of the first radial direction portion, 
 a second end portion that is located at the other end of the axial direction portion, 
 a second radial direction portion that projects radially outward from the second end portion of the axial direction portion and extends in the radial direction 
 perpendicular to the axis of the piston rod, 
 the first radial direction portion, the axial direction portion, and the second radial direction portion being molded together as a single press-molded product, 
 the axial direction portion constitutes a bottom wall of the seal installation groove, and 
 the second radial direction portion constitutes one of side walls of the seal installation groove. 
 
     
     
       2. The piston assembly according to  claim 1 , wherein:
 the piston main body includes a third piston member constituted from a plate-like member; and 
 on an outer peripheral portion of the piston main body, a support member or a magnet that extends along an outer circumference of the piston main body is disposed in a groove formed between the second piston member and the third piston member. 
 
     
     
       3. The piston assembly according to  claim 1 , wherein:
 the piston rod is joined as a first piston rod to one side of the piston main body by welding; and 
 a second piston rod is joined to another side of the piston main body. 
 
     
     
       4. The piston assembly according to  claim 1 , wherein:
 the first piston member and the second piston member are joined by welding. 
 
     
     
       5. The piston assembly according to  claim 1 , wherein the fitting portion is joined only with the surface of the second piston member located on the side of the second piston member that faces toward the first piston member. 
     
     
       6. The piston assembly according to  claim 1 , wherein a joining surface between the first piston member and the second piston member is coplanar with a joining surface between the piston rod and the second piston member. 
     
     
       7. A fluid pressure cylinder comprising:
 a piston assembly; and 
 a housing that accommodates the piston assembly therein movably in the axial direction, wherein: 
 the piston assembly comprises: 
 a piston main body; and 
 a piston rod joined to the piston main body, wherein: 
 the piston rod includes a cylindrical body portion; 
 the piston main body includes a first piston member and a second piston member which are constituted from plate-like members; 
 the first piston member and the second piston member are joined mutually under a condition of being superimposed in an axial direction of the piston rod; 
 a seal installation groove that extends in a circumferential direction is formed between an outer peripheral edge of the first piston member and an outer peripheral edge of the second piston member; and 
 a through hole is provided in the first piston member so as to penetrate in a plate thickness direction thereof; 
 the second piston member has, over the entirety thereof, a plate thickness that is smaller than an outer diameter of the piston rod; 
 a fitting portion is provided on a proximal end of the cylindrical body portion to project from the proximal end of the piston rod in the axial direction of the piston rod, the fitting portion being fitted in the through hole; 
 the fitting portion has an outer diameter which is smaller than that of the cylindrical body portion and the fitting portion has an end surface that is joined to the second piston member by welding, 
 the end surface of the fitting portion is joined with an end surface of the second piston member located on a side of the second piston member that faces toward the first piston member; the end surfaces of the fitting portion and the second piston member that are joined with each other are perpendicular to an axis of the piston rod; and 
 the outer diameter of the fitting portion is the same as, or slightly smaller than, the inner diameter of the through hole, 
 wherein one of the first piston member and the second piston member includes: 
 a first radial direction portion that extends in a radial direction perpendicular to the axis of the piston rod; 
 an axial direction portion that extends parallel to the axis of the piston rod, projects from an outer end of the first radial direction portion to a direction away from the other one of the first piston member and the second piston member, and includes 
 a first end portion that is located at an end connected to the outer end of the first radial direction portion, 
 a second end portion that is located at the other end of the axial direction portion, 
 a second radial direction portion that projects radially outward from the second end portion of the axial direction portion and extends in the radial direction 
 perpendicular to the axis of the piston rod, 
 the first radial direction portion, the axial direction portion, and the second radial direction portion being molded together as a single press-molded product, 
 the axial direction portion constitutes a bottom wall of the seal installation groove, and 
 the second radial direction portion constitutes one of side walls of the seal installation groove. 
 
     
     
       8. The fluid pressure cylinder according to  claim 7 , wherein the fitting portion is joined only with the surface of the second piston member located on the side of the second piston member that faces toward the first piston member. 
     
     
       9. The fluid pressure cylinder according to  claim 7 , wherein a joining surface between the first piston member and the second piston member is coplanar with a joining surface between the piston rod and the second piston member. 
     
     
       10. A method for manufacturing a piston assembly comprising:
 a first step of superimposing a first piston member and a second piston member which are constituted from plate-like members, and joining both members to obtain a piston main body; and 
 a second step of joining a piston rod to the piston main body, wherein: 
 a seal installation groove that extends in a circumferential direction is formed between an outer peripheral edge of the first piston member and an outer peripheral edge of the second piston member; and 
 wherein 
 a through hole is provided in the first piston member so as to penetrate in a plate thickness direction thereof; 
 the second piston member has, over the entirety thereof, a plate thickness that is smaller than an outer diameter of the piston rod; 
 a fitting portion is provided on a proximal end of a cylindrical body portion of the piston rod to project from the proximal end of the piston rod in the axial direction of the piston rod, the fitting portion being fitted in the through hole; 
 the fitting portion has an outer diameter which is smaller than that of the cylindrical body portion and the fitting portion has an end surface that is joined to the second piston member by welding, 
 the end surface of the fitting portion is joined with an end surface of the second piston member located on a side of the second piston member that faces toward the first piston member; the end surfaces of the fitting portion and the second piston member that are joined with each other are perpendicular to an axis of the piston rod; and 
 the outer diameter of the fitting portion is the same as, or slightly smaller than, the inner diameter of the through hole, 
 wherein one of the first piston member and the second piston member includes: 
 a first radial direction portion that extends in a radial direction perpendicular to the axis of the piston rod; 
 an axial direction portion that extends parallel to the axis of the piston rod, projects from an outer end of the first radial direction portion to a direction away from the other one of the first piston member and the second piston member, and includes 
 a first end portion that is located at an end connected to the outer end of the first radial direction portion, 
 a second end portion that is located at the other end of the axial direction portion, 
 a second radial direction portion that projects radially outward from the second end portion of the axial direction portion and extends in the radial direction 
 perpendicular to the axis of the piston rod, 
 the first radial direction portion, the axial direction portion, and the second radial direction portion being molded together as a single press-molded product, 
 the axial direction portion constitutes a bottom wall of the seal installation groove, and 
 the second radial direction portion constitutes one of side walls of the seal installation groove. 
 
     
     
       11. The method for manufacturing a piston assembly according to  claim 10 , wherein:
 in the first step, the first piston member and the second piston member are joined by welding. 
 
     
     
       12. The method according to  claim 10 , wherein the fitting portion is joined only with the surface of the second piston member located on the side of the second piston member that faces toward the first piston member. 
     
     
       13. The method according to  claim 10 , wherein a joining surface between the first piston member and the second piston member is coplanar with a joining surface between the piston rod and the second piston member.